Aneurysms and/or dissections may occur in blood vessels, and most typically occur in the aorta and peripheral arteries. Depending on the region of the aorta involved, the aneurysm may extend into areas having vessel bifurcations or segments of the aorta from which smaller “branch” arteries extend. Abdominal aortic aneurysms include aneurysms present in the aorta distal to the diaphragm, e.g., pararenal aorta and the branch arteries that emanate therefrom, including the renal arteries and the superior mesenteric artery (SMA). Abdominal aortic aneurysms are bulges or weakening regions in the aortic wall and are frequently classified by their location relative to the renal arteries. Referring to FIGS. 1A-1C, various types of abdominal aortic aneurysms are shown for illustrative purposes. In FIGS. 1A-1C, a portion of an aorta A is shown extending down to the aortic bifurcation in which aorta A bifurcates into the common iliac arteries, including a right iliac artery RI and a left iliac artery LI. A right renal artery RRA and a left renal artery LRA extend from aorta A, as does the superior mesenteric artery (SMA) which arises from the anterior surface of the abdominal aorta. In FIG. 1A, an infrarenal abdominal aortic aneurysm AAAI is located distal to the renal arteries. In FIG. 1B, a juxtarenal abdominal aortic aneurysm AAAJ approaches or extends up to, but does not involve, the renal arteries. In FIG. 1C, a suprarenal abdominal aortic aneurysm AAAS involves and extends above the renal arteries.
In some cases, the aneurysmal region of the aorta can be bypassed by use of an endoluminally delivered tubular exclusion device, e.g., by a stent-graft placed inside the vessel spanning the aneurysmal portion of the vessel, to seal off the aneurysmal portion from further exposure to blood flowing through the aorta. A stent-graft can be implanted without a chest incision, using specialized catheters that are introduced through arteries, usually through incisions in the groin region of the patient. The use of stent-grafts to internally bypass, within the aorta or flow lumen, the aneurysmal site, is also not without challenges. In particular, care must be taken so that critical branch arteries are not covered or occluded by the stent-graft, yet the stent-graft must seal against the aorta wall and provide a flow prosthesis for blood to flow past the aneurysmal site. Where the aneurysm is located immediately adjacent to the branch arteries, there is a need to deploy the stent-graft in a location which partially or fully extends across the location of the origin of the branch arteries from the aorta to ensure sealing of the stent-graft to the artery wall.
To accommodate side branches, main vessel stent-grafts having a fenestration or opening in a side wall thereof may be utilized. The main vessel stent-graft is positioned to align its fenestration with the ostium of the branch vessel. In use, a proximal end of the stent-graft, having one or more side openings, is prepositioned and securely anchored in place so that its fenestrations or openings are oriented when deployed to avoid blocking or restricting blood flow into the side branches. Fenestrations by themselves do not form a tight seal or include discrete prosthesis(s) through which blood can be channeled into the adjacent side branch artery. As a result, blood leakage is prone to occur into the space between the outer surface of the main aortic stent-graft and the surrounding aortic wall between the edge of the graft material surrounding the fenestrations and the adjacent vessel wall. Similar blood leakage can result from post-implantation migration or movement of the stent-graft causing misalignment between the fenestration(s) and the branch artery(ies), which may also result in impaired flow into the branch artery(ies).
In some cases, the main vessel stent-graft is supplemented by another stent-graft, often referred to as a branch vessel stent-graft or branch vessel stent-graft. The branch vessel stent-graft is deployed through the fenestration into the branch vessel to provide a prosthesis for blood flow into the branch vessel. The branch vessel stent-graft is preferably sealingly connected to the main vessel stent-graft in situ to prevent undesired leakage between it and the main vessel stent-graft. This connection between the branch vessel stent-graft and main vessel stent-graft may be difficult to create effectively in situ and is a site for potential leakage.
Particular issues arise in treating juxtarenal abdominal aortic aneurysms, as shown in FIG. 1B, and suprarenal abdominal aortic aneurysms, shown in FIG. 1C. Similar issues arise in treating so-called short-neck infrarenal aneurysms, in which only a small length (i.e., less than 10 mm) of non-aneurysed tissue is present between the renal arteries and the proximal end of the infrarenal aneurysm. Often, a proximal infrarenal neck or non-aneurysmal tissue of 10-15 mm length is usually required to allow endovascular repair of abdominal aortic aneurysms (EVAR). Since juxtarenal and suprarenal aneurysms extend up to or above the renal arteries, there is an insufficient non-aneurysmal length or neck of the aorta distally of (i.e., distal to or downstream of) the renal arteries for a stent-graft to deploy and seal against the vessel wall. Accordingly, it is necessary to deploy some of the stent-graft proximally of (i.e., above or upstream of) the renal arteries, which requires consideration of the superior mesenteric artery (SMA) and not to occlude or block blood flow thereto. Due to variations in patient anatomy, short-neck infrarenal, juxtarenal, and suprarenal aneurysms are typically treated with open repair or a custom designed, fenestrated endovascular stent-graft. Custom designed stent-grafts require a significant lead time, i.e., 6-8 weeks, and are costly to design and manufacture.
Thus, there remains a need in the art for improvements in stent-graft structures for treating abdominal aortic aneurysms that require directing flow from the aorta into branch vessels emanating therefrom, such as the renal arteries and the superior mesenteric artery (SMA).